The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Modern internal combustion engines are equipped with sophisticated systems to monitor and control various aspects of engine performance during ongoing operation, to meet operator demands for performance, including torque and fuel economy, and to satisfy government regulations related to emissions, safety, and fuel economy. Such systems include sensing devices and actuators connected to one or more control modules which execute computer programs to monitor and control engine operation during ongoing operation.
Exhaust gas temperature is an important parameter used by engine system designers. By way of illustration of a need for an accurate determination of exhaust gas temperature, emissions requirements have led to implementation of exhaust gas recirculation (EGR) systems combined with aftertreatment systems to reduce engine emissions. Control of exhaust gas recirculation requires an accurate determination of EGR mass flow. Such methods include calculating EGR flow from a gas flow equation through an orifice, and, determining a difference between charge air mass flow and fresh air mass flow. Such calculations use engine exhaust pressure as one of the input variables. Some engine manufacturers have implemented an exhaust pressure sensor to determine exhaust pressure, while others have considered exhaust pressure estimation. A typical calculation of EGR flow is as follows, in Eq. 1:
                                          m            .                    egr                =                  C          *          A          *                                    P              ex                                                      R                *                                  T                  egr                                                              ⁢                      f            (                                          P                im                                            P                ex                                      )                                              [        1        ]            
wherein Pex comprises exhaust pressure, Pim comprises intake manifold pressure, Tegr is EGR gas temperature exiting from an EGR cooler; C is a discharge coefficient, and, A comprises valve affected area. Determination of the exhaust pressure Pex through estimation requires some knowledge of exhaust gas temperature input to perform the estimation.
Furthermore, diagnostic regulations for diesel engines require detection of fouling or plugging of an EGR gas cooler when it causes increases in engine emissions. To monitor EGR cooler fouling, it often requires knowledge of EGR gas temperatures into and out of the EGR cooler. The EGR gas temperature into the EGR cooler is the exhaust gas temperature.
Exhaust gas temperature monitoring can be used to provide other operations. These include a feedback control system for protecting exhaust components, including a turbine for a turbocharged system. Exhaust gas temperature monitoring can also be used in managing exhaust gas feedstream temperature to various emissions devices implemented on a vehicle.
It may be preferable to estimate exhaust gas temperature to reduce system costs, including costs for the sensor and wiring harness. Furthermore a system which implements a physical sensor to measure exhaust gas temperature is required to monitor operation of the sensor for faults, adding further complexity to the system.
Current algorithmic models to determine and estimate exhaust gas temperature comprise non-linear models which require significant computational resources and affect throughput of an on-board control module. Furthermore, empirical models for a conventional combustion system are not readily adapted to work with systems utilizing premix charge ignition (PCI) combustion having high EGR flow rates.
Therefore, there is a need to estimate exhaust gas temperature for an internal combustion engine which addresses the above.